How to Prune Young Locust Trees

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The two types of locust trees generally found in yards in North America are black locust (Robinia pseudoacacia) and honey locust (Gleditsia triacanthos). Both species thrive in U.S. Department of Agriculture plant hardiness zones 3 through 8. While both species are thorny, some cultivars of the honey locust are thornless. To prevent locust trees from growing into thorny thickets, young trees should be pruned to encourage a single trunk. Unlike most shade trees, locust trees are pruned after they bloom, in early summer, to prevent excessive bleeding of the sap.

1

Put on heavy gloves and safety glasses before pruning the locust tree. Also wear boots, long sleeves and long pants to protect yourself from the tree's sharp thorns, and errant twigs and branches.

2

Remove dead or broken branches with anvil pruners or loppers. Anvil pruners are used on branches less than 1/2 inch in diameter, while loppers are used on branches up to 2 inches in diameter.

3

Disinfect the pruning tools between each cut with a solution of equal parts rubbing alcohol and water. Honey locust trees are especially prone to fungal infections; disinfecting the tools helps prevent the spread of disease.

4

Cut off all the suckers around the base of the tree and sprouting from the roots. Black locust trees tend to develop multiple trunks and a thicketlike growth if not pruned to maintain a single trunk form.

5

Trim back the small lower branches that will be removed as the tree matures. Locust trees grow in a rounded form; the lowest branches are removed before they're 2 inches in diameter.

6

Remove crowded or crossing branches, and water sprouts to open up the tree's interior for air circulation. Water sprouts grow rapidly upward from the tree's branches and may overwhelm the form of the tree.

7

Select the branches that will remain as scaffolding branches as the tree grows, and remove the smaller branches in between them. Scaffolding branches are spaced 18 to 24 inches apart.

8

Rake up the dead leaves, twigs and debris under the tree, and put it in the green bin for trash pickup. While you can compost the debris, the thorns may take longer to decompose and make your compost difficult to handle even while wearing gloves.

Things You Will Need

Heavy gloves

Safety glasses

Anvil pruners

Loppers

Bucket

Rubbing alcohol

Rake

Tips

Cut branches back to the branch collar, which is the thickened section where the branch attaches to the tree's trunk.

As the tree grows taller, remove the lower branches that you trimmed back, before they're 2 inches in diameter.

Shade trees are pruned so the lowest branches are 7 to 10 feet above the ground, while street trees are pruned to 14 feet above the pavement.

Warnings

Keep all tools and disinfectants out of reach of children and pets.

Use caution when working around the locust tree; the thorns are extremely sharp and puncture wounds may become infected.

Never top the main trunk of a tree; if it will interfere with power lines when mature, select a smaller tree species.

About the Author

With degrees in fine and commercial art and Spanish, Ruth de Jauregui is an old-school graphic artist, book designer and published author. De Jauregui also worked in the Napa Valley as a high-end catering assistant. She enthusiastically pursues creative and community interests, including gardening, home improvement, pet rescue and social issues.